(1) Field of the Invention
The present invention relates to a film image projecting apparatus such as a microfilm reader and a microfilm printer for retrieving desired information by searching blip marks arranged laterally of frames in a roll film.
(2) Description of the Prior Art
Generally, a film image projecting apparatus such as a microfilm reader and a microfilm printer utilizes a roll film having blip marks arranged laterally of frames. The blip marks are optically detected and counted up for automatic retrieval of a desired frame in the roll film.
FIGS. 1A through 1C of the accompanying drawings illustrate three typical examples of roll film used with the above image projecting apparatus.
As shown in FIG. 1A, the first roll film includes one frame FF transversely thereof containing one image, and a blip mark M disposed laterally of each frame FF. This type of roll film is commonly known as simplex film.
As shown in FIG. 1B, the second roll film includes frames divided into two rows extending longitudinally of the film, and blip marks M arranged along opposite lateral sides thereof. This type of roll film is commonly known as duofilm. One of the two rows is called A-channel CA and the other B-channel CB. The duofilm has a continuous image photographed into frames FFA in A-channel CA, and then the film is reversed for photographing a different continuous image into frames FFB in B-channel CB. Thus, a plurality of mutually related continuous images may be retrieved from the duofilm.
As shown in FIG. 1C, the third roll film includes frames divided into two rows extending longitudinally of the film, and blip marks M arranged along one lateral side thereof. This type of roll film is commonly known as duplex film. As in the case of duofilm, the two rows are called A-channel CA and B-channel CB. The duplex film has a plurality of mutually related continuous images photographed into the frames in the order of FFA, FFB, FFA, FFB and so on.
When the roll film F is illuminated by an exposure lamp or other light source, an illuminated area is formed on the roll film F which is projected in magnification onto a photoreceptor drum to form an electrostatic latent image thereon, or displayed in magnification on a screen. In this connection, known film image projecting apparatus have the following drawbacks:
(1) As noted above, the duplex film has mutually related continuous images photographed into the frames in the order of FFA, FFB, FFA, FFB and so on. Therefore, when copying these images onto recording paper P continuously, it is necessary to move the roll film F in transverse directions thereof for copying each frame.
Conventionally, the roll film F is moved transversely manually by means of a knob or a handle or by operating a specially provided frame select switch. Such a control operation is troublesome, prone to miscopying, and inefficient.
(2) The duofilm and duplex film include two frames FFA and FFB arranged transversely thereof, and hence two centers of the images (see FIGS. 1B and 1C). The image projecting apparatus are constructed to project images in magnification to the screen such that normally the center CO of the simplex film (see FIG. 1A) coincides with the center of the screen. Therefore, when projecting the images contained in frames FFB of the duofilm or duplex film, it is necessary to move the roll film F transversely as above.
However, when the roll film F is moved transversely, the blip marks M on the roll film tend to move out of the illuminated area to the detriment of information retrieval.
(3) Generally, the illuminated area has a light quantity distribution as illustrated in FIG. 2, in which a region adjacent the center of the roll film F is brightly illuminated whereas peripheral regions adjacent blip marks M are less brightly illuminated. Moreover, the light intensity is reduced as a whole when the images are projected in magnification. Therefore, even in the case of simplex film having blip marks M included in the illuminated area, regions of blip marks M are only dimly illuminated thereby causing a blip mark sensor to make errors in detecting the blip marks M.
(4) In the case of reader-printer having a read mode and a print mode and when switching is made to the print mode with the roll film F projected in magnification, an uneven intensity of illumination due to the light distribution results in poor quality copy images.